Electric fuse and fuse terminals



May 4, 1937. M. B. woon ELECTRIC FUSE AND FUSE TERMINALS Filed Aug. 3, 1955 Patented May 4, 1937 UNITED STATES PATENT OFFICE The Chase-Shawmut Company, Newburyport, Mass., a corporation of Massachusetts Application August 3,

1l Claims.

This invention relates to electric fuses of the cartridge type having knife blade terminals; and to the terminals of such fuses.

In the type of renewable electric fuses of the cartridge type having knife blade terminals, the

terminal blades are connected by a rigid insulating bar and may be spaced from said bar by rectangular spacer plates interposed therebetween. The blade terminals also have discs thereon by which the terminal structure is clamped in position within the enclosing casing. Heretofore the discs have been secured to the knife blades by a so-called staking process which upsets material of the knife blade against a face of the disc and often leaves projecting material that is inter- Dosed between the disc and the end of the insulating connecting bar or spacer plate and prevents the plate and bar from abutting firmly against the inner face of the disc which is desirable for the purpose of holding the parts in rm alignment.

It is an object of the present invention to secure the disc to the knife blade in such manner that there is no projecting material adjacent the junction between the disc and its knife blade so that the square end of the insulating connecting bar or the square end of the spacer plate can be abutted firmly against the disc and by the disc be held against annular displacement with respect to the knife blade.

A further object of the invention consists in securing the disc to the knife blade by forming the disc with a slot for the knife blade and projecting material of the disc outwardly of a face thereof at the slot and, when the disc is on the blade, then forcing the relatively hard projecting material inwardly and into the slot and thereby compressing the material into firm engagement with the blade. When the disc is composed 40 of iron or steel and the knife blade is copper, as is frequently the case, the hard material of the disc is forced into the knife blade.

Another object of the invention is the provision of a cartridge type fuse of the knife blade type having a disc on the knife blade which is secured to the knife blade by material of the disc that has been embedded into the knife blade, the disc being composed of a harder material than the knife blade.

A further object is generally to improve the construction of electric fuses.

Fig. 1 is a longitudinal sectional view through a renewable electric fuse of the cartridge type embodying the present invention.

1935, Serial No. 34,567

Fig. 2 is a plan view of the removable structure of Fig. 1.

Fig. 3 is a longitudinal sectional view through one of the knife blade terminals and discs thereon.

Fig. 4 is an end view of the knife blade terminal 5 of Fig. 3.

Fig. 5 is a longitudinal sectional View through the other knife blade terminal and disc thereon.

Fig. 6 is a sectional detail of a knife blade terminal and a disc therefor prior to the compression of the disc upon the terminal.

Fig. 7 is a perspective view of a terminal disc for use in connection with a knife blade.

Fig. 8 is a perspective view of the terminal blade and disc of Fig. 5.

Fig. 9 is a perspective View of a terminal blade of Fig. 3 illustrating the manner in which the disc forms a locking groove in the blade.

Figi. l0 is a sectional detail illustrating the manner of compressing the disc into contact with the blade.

Fig. l1 is a perspective view of a spacing member interposed between a knife blade and the insulating connecting bar of Fig. 1.

As illustrated in Fig, 1 the renewable cartridge type electric -fuse of the knife blade type embodying the present invention comprises a tubular enclosing casing I4 commonly of insulating material, as fibre, having external screw threads I6 on its opposite ends which are engaged with interiorly and exteriorly screw-threaded thin metal ferrules I8 permanently attached to the casing. End caps 20 and 22 are screw-threaded removably on the ferrules. The end wall of the end cap 20 is provided with an elongated slot adapted to fit and to u receive a knife blade terminal 24. The end wall of the end cap 22 is provided with a circular aperture 26 through which the knife blade terminal 28 is freely extended. Both knife blades are provided with intermediately positioned opposite shoulders 3U and inner tongues 32, see especially Fig. 9, of reduced width which extend into the interior of the casing. The knife blades are secured to the opposite ends of the same face of a relatively rigid connecting and spacing bar 34 of insulating material, as fibre, by suitable means as screws 36 which pass through the connecting bar and are screw-threaded into threaded apertures 38 of the tongues 32 of the knife blades. For some fuses spacer plates 40, see Figs. 1 and l1, 50 usually of rectangular construction, are interposed between the connecting bar and the knife blades, the attaching screws 36 passing loosely through thread-free apertures 42 in the spacer plates. Each knife blade tongue has a linkclamping screw or equivalent 44 that is screwthreaded into an aperture 46 of the tongue and by which an end of the fusible link 48 is adapted to be clamped removably to the knife blade. Each spacer plate 40 has a clearance aperture 50 that receives the end of the screw 44. The knife blades 24 and 28 carry blade-centering discs 52 and 5d which t closely within the opposite ends of the enclosing tube i4 and serve to position the knife blade structure therein. rI'he peripheral portions of the discs are provided with notches 56 through which the pressure gases formed within the interior of the fuse casing upon the blowing of the fuse link can pass into the end caps 20 and 22 and thence escape to the atmosphere through the screw threads of the end caps and ferrules or through other suitable venting means. rhe knife blade 28 is provided with a second disc 52 which is diametrically larger than and is in contact with the disc 54 and confronts and has parts that abut against the end of the enclosing casing. The end cap 22 serves to clamp the disc 58 forcibly between it and the end of the fuse casing thereby to retain the knife blade structure removably in position within the enclosing casing. The fuse as thus described is now well known in the art.

With a fuse constructed as described it is desirable to abut the flat ends of the connecting bar 34 and spacer plates 40 squarely against the inner faces of the discs 52 and 54 so as to preserve the parallel alignment of the connecting bar and knife blade terminals and to prevent angular displacement or rotation of the spacer plates; and the present invention is concerned With securing the discs to the knife blades in such manner that this can be done readily. The knife blades 24 and 28 are composed of copper or other relatively soft metal as compared with the discs 52 and 54, which commonly although not necessarily, are of iron or steel. rIhe manner of securing the discs 52 and 54 to the knife blades is identical and the manner of securing the disc 52 to the knife blade 24 will be described. The disc 52 is provided with a generally rectangular slot 60 therethrough of such dimensions as to permit the free passage of the tongue 32 of the knife blade so that the disc can be passed over the tongue and be seated against the shoulder 30 of the knife blade. In forming the slot 60 the material of the disc is displaced outwardly of the inner face thereof by a piercing operation so as to form a pair of projecting parallel lips 62 which bound the long edges of the slot, as is clearly shown in Figs. 6, 7 and 10, the long inner faces of the slot being generally parallel as the piercing punch which forms the slot is straight sided. The dimensions of the slot are such that while the tongue of the knife blade can pass freely into the slot there is no unnecessary looseness between the tongue and the disc. After the disc has been placed upon the tongue and is seated upon the shoulders 30 the lips S2 are forced inwardly or toward the body of the disc thereby to cause the material to flow into the slot and to cause the disc to grip the knife blade firmly whereby to lock the knife blade and disc permanently and rigidly together and to provide the disc with a smooth inner face free from projections. When the disc is harder than the knife blade, the displaced material is forced into the body of the knife blade as in Figs. 3 and 5.

The manner of forcing the disc into engagement with the knife blade is illustrated in Fig. 10. The outer or enlarged portion of the knife blade is placed in a slot of a lower die block 64 with the disc resting upon the top face of the block. The tongue of the knife blade extends loosely into a slot 66 of an upper die block 68 which closely fits over the tongue and engages the lips B2 of the disc. The upper die block 68 is moved forcibly toward the lower block and forces the material of the lips 62 back into the disc and into the slot and thereby compresses it against the knife blade. When the disc is of iron the lips are forced into the body of the knife blade, as illustrated in Figs. 3 and 5. The lips displace the knife blade material to form a transverse channel 1D, see Fig. 9, in which the lips are embedded, thus securely anchoring the disc to the knife blade against movement in either direction. The die block 68 flattens the inner face of the disc so that there is no projecting part. Thus the end of the connecting bar 34 and also an end face of the spacer plate 40 can abut directly and firmly against the inner L face of the disc as illustrated in Fig. 1 and be thereby held in parallelism with the knife blades.

The disc 54 is secured to the knife blade 28 in a similar manner except that the larger disc 58 is seated upon the shoulder of the knife blade and is interposed between the shoulders and the disc 54. I'he attachment of the disc 54 to the knife blade securely locks the disc 58 in place thereon.

I claim:

1. An electric fuse of the cartridge type having an enclosing casing, knife blade terminals, an insulating bar connecting said terminals, bladecentering discs on said knife blades at the ends of said bar and within the ends of and closely fitting the interior of said casing, and means fixing a disc rigidly on its associated knife blade whereby at the junction therebetween the surfaces of both that confront said bar are free from projecting parts, the end of said connecting bar being abutted against the face of the disc.

2. An electric fuse of the cartridge type having an enclosing casing, knife blade terminals, an insulating bar connecting said terminals, a spacer plate on a face of a knife blade terminal having a flat end face interposed between the knife blade terminal and said bar, blade centering discs on said knife blades at the ends of said plates and bars and within the ends of and closely fitting the interior of said casing, and means rigidly aflixing a disc on its knife blade so that the surfaces of the knife blade and the disc at the junction therebetween are free from a projecting part, and the flat end faces of said spacing plate and bar being seated against the face of said disc.

3. An electric fuse of the cartridge type having an enclosing casing, knife blade terminals, means on said terminals for attaching the ends of a fuse link thereto, a blade centering disc in said casing and on at least one of said terminals having a part that is compressed upon said terminal to provide said disc with a flat inner face square with its blade, and an insulating bar connecting said terminals having a square end which is seated against said end face and on said knife blade.

4. An electric fuse of the cartridge type having an enclosing casing, knife blade terminals, means on said terminals for attaching the ends of a fuse link thereto, a blade centering disc in said casing and on at least one terminal having a. part that is imbedded into the terminal to attach the disc thereto and provide the disc with a. fiat inner face square with the blade, an insulating bar connecting said terminals, a spacer plate interposed between said bar and said disc carrying terminal and on said terminal, said spacer plate having a flat end face that is seated against the fiat inner face of said disc.

5. A knife blade terminal structure for a cartridge type electric fuse comprising a knife blade having means for attaching the end of a fuse link thereto, and a disc thereon having a slot in which said blade is located, said disc having a lip at a long edge of said slot and at one face of said blade which is imbedded into said knife blade, said face being free from irregularities and projections in the region of its junction with said blade.

6. A knife blade terminal structure for a cartridge type electric fuse comprising -a knife blade having a tongue, said tongue having means for attaching thereto the end of a fuse link, a blade centering disc having an elongated slot in which said tongue is located, said disc having a pair of confronting, originally outstanding, lips which form the opposite long edges of the slot and are located on opposite sides of said blade and are compressed inwardly of the disc and slot and upon said knife blade and prevent displacement of said disc in at least one direction on said knife blade, and said knife blade having a shoulder against which the lip-free face of said disc abuts to prevent displacement of said disc in the opposite direction.

'7. A knife blade terminal structure for a cartridge type electric fuse comprising -a knife blade having a tongue, said tongue having means for attaching thereto the end of a fuse link, a disc having a slot in which said tongue is located, and a pair of confronting lips which form the opposite sides of the slot on one face of the disc and are extended into said tongue, and shoulders on said knife blade abutting said disc on the lipfree face thereof.

8. A cartridge type electric fuse having a knife blade terminal, means for attaching the end of a fuse link to said terminal, a disc having a slot therethrough in Which the terminal is located, said disc having a pair of confronting lips at the long edges of the slot which extend into said terminal and anchor said disc and terminal together, said lips being inset into said disc and slot and the lip face of said disc being smooth and free from a projecting lip and an insulating bar attached to said terminal and abutting the lip face of said disc.

9. A knife blade terminal structure for a cartridge type electric fuse comprising a copper knife blade terminal, an iron disc having a slot through which said terminal is extended, said disc having a pair of confronting lips at the opposite long edges of said slot at one face of the disc, said lips being imbedded into said terminal.

10. A knife blade terminal structure for a cartridge type electric fuse comprising a knife blade having a transverse groove in a face thereof, a disc having a slot in which said knife blade is located, and a lip forming a long edge of said slot and located in said groove.

11. A knife blade terminal structure for a cartridge type electric fuse comprising a knife blade having a transverse groove in a face thereof, a disc having a slot in which said knife blade is located, and a lip forming a long edge of said slot and located in said groove, said lip being forced into said knife blade and said groove being formed by the displacement of knife blade metal by said lip.

MORRIS B. WOOD. 

